1. Field of the Invention
This invention relates to a novel N-sulfonyloxyimide compound suitable as a radiation-sensitive acid-generating agent component of radiation-sensitive resin compositions used as chemically amplified resists suited for fine processing made by various radiations such as ultraviolet radiations, far-ultraviolet radiations, X-raditions and charged particles. It also relates to chemically amplified positive and negative radiation-sensitive resin compositions making use of such an N-sulfonyloxyimide compound.
2. Description of the Prior Art
In the field of fine processing as typified by the fabrication of integrated-circuit devices, the size of processing in lithography is being made finer in order to achieve a higher degree of integration. In recent years, lithographic processes that enables stable fine processing in a size of 0.5 xcexcm or finer is powerfully being developed.
However, in conventional processes making use of visible radiations (wavelength: 400 to 700 nm) or near ultraviolet radiations (300 to 400 nm), it is difficult to form such fine patterns in a high precision. Accordingly, proposed are lithographic processes that can achieve a wider focal depth and make use of radiations having a short wavelength (wavelength: 300 nm or shorter) effective for making design rules finer.
Radiations having such a short wavelength may include, e.g., far-ultraviolet radiations of KrF excimer lasers (wavelength: 248 nm) or ArF excimer lasers (wavelength: 193 nm), X-radiations such as synchrotron radiations, and charged-particle radiations such as electron radiations. Then, as a high-resolution resist adaptable to these short-wavelength radiations, xe2x80x9cchemically amplified resist resistxe2x80x9d is proposed by International Business Machine (IBM) Corp. At present, improvements of this chemically amplified resist are being energetically made.
Chemically amplified resists are resists with which a resist pattern is formed by generating an acid by irradiation with radiations (hereinafter xe2x80x9cexposurexe2x80x9d) to a radiation-sensitive acid-generating agent contained therein to cause a chemical change (e.g., change in polarity, destruction of chemical bonds, or cross-linking reaction) in resist film by the catalytic action of this acid and utilize a phenomenon that the solubility to a developing solution changes at the exposed areas.
In such chemically amplified resists, the radiation-sensitive acid-generating agent is known to have a great influence on the function as a resist, and is commonly grouped into an ionic one and a nonionic one. Radiation-sensitive acid-generating agents comprised of N-sulfonyloxyimides, which are nonionic, have a good solubility in non-polar or medium-polar solvents which are widely used in resists, and products formed after exposure are well soluble in water-based alkaline developing solutions. Radiation-sensitive acid-generating agents for chemically amplified resists are widely used in the form of a single agent or a mixture with other photo-acid-generating agent.
Now, N-sulfonyloxyimides are grouped into the following three types by the types of sulfonic acids corresponding thereto.
Sulfonyloxyimides generated from superacids (3-1) and (3-2): 
Sulfonyloxyimides generated from aromatic sulfonic acids (3- 3) and (3-4): 
Sulfonyloxyimides generated from aliphatic sulfonic acids (3-5) and (3-6): 
It, however, does not follow that these N-sulfonyloxyimides can satisfy all performances required in chemically amplified resists. More specifically, sulfonyloxyimides generated from superacids are fluorine-substituted and hence the acid generated has so low a boiling point as to have a possibility that the acid volatilizes at the time of baking to corrode an exposure assembly, and also has so high a chemical activity as to make it difficult to control side reaction at the time of protective group elimination reaction and cross-linking reaction. They have such disadvantages or besides, since they are esters of superacids, have a poor stability. Also, the sulfonyloxyimides generated from aromatic sulfonic acids have is disadvantages that they show so great a absorption in the wavelength region of far-ultraviolet radiations as to tend to cause a lowering of resolution performance.
On the other hand, the sulfonyloxyimides generated from aliphatic sulfonic acids have a relatively high transparency to far-ultraviolet radiations and the acid generated has an appropriate strength to enable relatively easy control of side reaction. Hence, they are especially useful among N-sulfonyloxyimide type radiation-sensitive acid-generating agents, as a component that compensates their disadvantages when used alone or in the form of a mixture with other radiation-sensitive acid-generating agent(s).
However, known aliphatic sulfonic acids, in particular, commercially readily available aliphatic sulfonic acids are limited, and hence no energetic studies have ever been made on the aliphatic sulfonyloxyimides. As an exception, N-sulfonyloxyimide compounds of a long-chain alkylsulfonic acid type and of a camphor sulfonic acid type are available. These compounds, however, have the following disadvantages. That is, the long-chain alkylsulfonic acid type sulfonyloxyimide compound greatly differs in polarity between sulfonyloxyimide moiety and long-chain alkyl moiety. Hence, it acts like a surface-active agent and, when added in a usual quantity as the radiation-sensitive acid-generating agent, microscopic air bubbles may be formed in the resist to bring about a possibility of greatly causing faulty coating or faulty development (or development defects). As for the camphor sulfonic acid type sulfonyloxyimide compound, it does not have such a problem, but a problem on stability remains unsettled. Since N-sulfonyloxyimide compounds are highly reactive sulfonyl esters, nucleophilic substitution reaction tends to take place. They may react with nucleophilic groups of other components in the resin, as exemplified by phenolic hydroxyl groups in a resin component and hydroxyl groups in a solvent component, or with water or the like remaining in a trace quantity in the resist, to become decomposed to cause a change in performance such as sensitivity of the resist. Even the camphor sulfonic acid type N-sulfonyloxyimide compound has such a disadvantage.
Accordingly, it has been earnestly sought to bring forth an N-sulfonyloxyimide compound which has a structure suited for commercial-scale manufacture, has no problem of volatilization or side reaction, can keep dark reaction from taking place during the storage of resist solutions and also is suitable as a radiation-sensitive acid-generating agent component of chemically amplified resists having a high resolution suited for fine processing.
Taking account of the above circumstances in the prior art, an object of the present invention is to provide a novel N-sulfonyloxyimide compound which has a structure suited for commercial-scale manufacture, especially can generate an acid in a good efficiency as having a high sensitivity (low exposure energy quantity) to far-ultraviolet radiations and charged-particle radiations, has no problem of volatilization or side reaction, can keep dark reaction from taking place during the storage of resist solutions and also is suitable as a radiation-sensitive acid-generating agent component of radiation-sensitive resin compositions used as chemically amplified resists having a high resolution suited for fine processing.
Another object of the present invention is to provide superior chemically amplified positive and negative radiation-sensitive resin compositions making use of such an N-sulfonyloxyimide compound.
According to the present invention, the above objects can firstly be achieved by an N-sulfonyloxyimide compound represented by the following general formula (1): 
wherein in the general formula (1), X represents a single bond or a double bond, Y and Z each independently represent a hydrogen atom or a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, or Y and Z combine to form an alicyclic structure or heterocyclic structure; and R is a group represented by the following general formula (2): 
wherein in the general formula (2), X1 represents an organic group having an ester linkage, having 2 to 10 carbon atoms, and, when X1 is present in plurality, X1""s may be the same with or different from each other; R1 represents an alkyl group having 1 to 10 carbon atoms or an alkoxyl group having 1 to 10 carbon atoms, and, when R1 is present in plurality, R1""s may be the same with or different from each other; and m is an integer of 1 to 11 and n is an integer of 0 to 10, satisfying m+n xe2x89xa611.
(Hereinafter often xe2x80x9cfirst inventionxe2x80x9d).
According to the present invention, the above objects can secondly be achieved by a chemically amplified positive radiation-sensitive resin composition comprising (A) a radiation-sensitive acid-generating agent comprising the N-sulfonyloxyimide compound represented by the above general formula (1), and (B) an alkali-insoluble or alkali-slightly-soluble resin protected with an acid-cleavable group, the resin being capable of turning soluble in alkali upon cleavage of the acid-cleavable group (hereinafter often xe2x80x9csecond inventionxe2x80x9d).
According to the present invention, the above objects can thirdly be achieved by a chemically amplified negative radiation-sensitive resin composition comprising (A) a radiation-sensitive acid-generating agent comprising the N-sulfonyloxyimide compound represented by the above general formula (1), (C) an alkali-soluble resin and (D) a compound capable of cross-linking the alkali-soluble resin in the presence of an acid (hereinafter often xe2x80x9cthird inventionxe2x80x9d)